The present invention relates to an apparatus and a method for scanning any manner of conveyed products with a light beam, particularly a laser, in order to detect and remove impurities or irregular bodies in the stream of products.
Laser scanners or sorters are known in the art. For example, Belgian Electronic Sorting Technology (BEST) manufactures and markets (not in the U.S.) laser sorters identified as the LS9000 and the ARGUS. The LS9000 utilizes a combination of lasers to produce narrow beams of light to detect even slight variations between products according to their structure and/or color. Another company, Barco, manufactures and sells a line of laser sorting machines, including the ES6000i and ES VI720, advertised as capable of sorting products by color and texture. The fundamental principles of laser sorting technology are well known and understood by those skilled in the art.
U.S. Pat. Nos. 4,634,881 and 4,723,659 describe and claim embodiments of laser sorters. The '881 patent describes a device that utilizes a laser for directing a concentrated light beam in a scanning pattern through which translucent bodies are conveyed. A background device is spaced from the laser and is illuminated by a separate source of light independent of the laser beam. A receiver receives the light reflected from the background member and from the translucent bodies moving through the laser scanning beam, as well as the light from the independent light source that illuminates the background member. The receiver produces an output signal that changes when an impurity enters the concentrated scanning light beam. This signal is used to operate a device that removes the impurity from the stream of translucent bodies.
The '659 patent relates to a similar device and includes transport devices for moving a plurality of rows of translucent bodies, such as french cut potatoes, through the light beam. The transport devices are configured to move parallel rows of the translucent bodies simultaneously through the light beam path. The background element is not separately illuminated and is formed of a material that causes impinging light from the laser to be diffused within the background element in a manner similar to diffusion of the light in a translucent body. A receiver has a field of view larger than the cross-sectional area of the light beam and receives the light reflected from the background element and from the translucent bodies moving through the light beam. The receiver is made insensitive to light in the part of its field of view that corresponds with the point of impingement of the light beam on the translucent bodies. The receiver includes a photosensitive detector wherein the optical center point of the detector is made blind by means of a black spot so that the detector will not “see” the light reflected from the point of impingement of the laser beam on the translucent bodies. The patent describes that the detector may also receive reflected light from a mirror having a small hole defined therethrough that corresponds to the point of impingement of the laser beam on the translucent bodies. Thus, the reflected light from the point of impingement passes through the small hole in the mirror and is not reflected to the detector.
The present invention relates to an improvement upon the known systems and methods for sorting and scanning products with laser beams and provides distinct advantages over the conventional systems and methods.